For the purpose of endowing golf balls with better rebound or resilience, a number of efforts have been made to tailor the formulation of materials for a golf ball. In addition to better rebound, golf balls are required to have many other properties including a soft feel on impact and durability. It is important to achieve a better profile of such properties. To maintain high resilience over a wide temperature range is one of important requirements on golf balls.
The same assignee as the present invention proposed in JP-A 2001-170213 (U.S. Ser. No. 09/732,786) and JP-A 2002-331046 a golf ball which is easy to mold and maintains stable softness and high resilience over a wide temperature range, more specifically a golf ball comprising a portion formed of a composition for a golf ball having blended therein at least one of a silicone rubber powder, a silicone resin powder, and a composite powder thereof. Although this golf ball has established stable rebound over a wide temperature range, there is still a desire to have a golf ball having higher rebound. JP-A 2001-353233 discloses another technique of compounding a powdery silicone component in a material for a golf ball. These compositions still fail to meet the requirements of golfers.
With respect to the compounding of silicone components in materials for golf balls, JP-A 60-258236, JP-A 61-258844, and JP-A 8-243191 also disclose attempts to blend millable silicone rubber with polybutadiene or cover-forming resin wherein the resulting material is subject to peroxide crosslinking. However, it is difficult to achieve a fine dispersion of silicone rubber in polybutadiene rubber or a fine dispersion of polybutadiene rubber in silicone rubber. From the aspects of improving the flow (or injection moldability) of a blend of these two components during golf ball molding that is closely related to the morphology of the blend and the durability of the resulting golf ball, there is a need for a technique capable of accomplishing a better dispersion of the two components.